Real-World examples of Reflection - reflection

What are your best examples of using Reflection in production code?

ASP.NET MVC inferring the action and controller to invoke from URL. Routing in general.

Most recently, I had to use reflection to load an assembly (in order to investigate its public types) from just the path of the assembly.

Before Linq To Sql came out...I had to write my own ORM in .NET 2.0.
I used reflection heavily to reflect back on:
Classes to their CRUD stored procedures
Properties to their column names
Which operations were valid for the class
I also used reflection to handle all variable assignment after the results were retreived (all classes inherited an ActiveRecord class that handled the calls into the DAL).
Rough stuff...but after some performance tuning it wasn't half bad.

Pulling data out of an SQL table where you had an ID, a type, and other data
Then you could load "Chevrolet" and work with all of it's methods

I did have occasion to write a Python O/R mapper on one at one point, but it was a proof of concept and never went into production.
I do quite a lot of work that makes extensive use of the system data dictionary on a DBMS (for example a generic slowly-changing dimension loader). It might be argued that this is not dissimilar to reflective programming in principle.
Finally, Python in all its forms is very easy to do reflection with. In fact, it's so good at this that I've used it to poke about with underlying API's in other languages - and use the reflective capabilities to query the underlying interfaces. I have done this with pretty much every reflective mechanism that exists in the Python world: CPython on Python API's and COM API's using makepy, Jython for java API's and IronPython for .Net API's.

In one of my recent apps, an add-in for Kofax Express, I have an option to OCR a file and output a PDF. Since the OCR tool I'm using has a runtime fee, I made the OCR part a seperate assembly. If the file exists, I show the OCR options and late bind the assembly and invoke the required methods and attach to the events with reflection. A simple plug in architecture without interfaces, and saves customers from having to pay royalty fees if they don't need to OCR; we just don't give them the OCR dll.

WPF Databinding:
1) Binding path "(TextBox.Text)" vs "Text"?
If you bind to a path called Text, WPF uses reflection to resolve the name. If you use the class-qualified name, binding avoids the reflection performance hit. Class-qualified names also allows binding to attached properties!
(via http://dotnet.org.za/rudi/archive/2008/03/25/10-things-i-didn-t-know-about-wpf-data-binding.aspx)

NUnit Unit Testing Framework - Not very typical though
CSLA uses reflection a lot
Pretty much any Windows Forms app that supports plugins

My DAL is all reflection based. It reflects on the POCO properties to build SQL.

Within a factory, we use reflection to either pass back a "Dummy" implementation of an interface or a real (hooked to the DB) implementation of an interface, based on the class specified in a properties file (in Java).

Related

How to persist application state in a WinRT app using Caliburn.micro?

I'm using Caliburn micro with a WinRT application and it looks like that there's no StorageManager class, anyone has suggestions about how to persist application/ViewModels state in this case.
TIA
This is not related to Caliburn.Micro but rather a general issue. You can either use Serialization but then you will have to pay attention to versioning and changes in your view model or you could save the fields you are interested in to a file using the normal IO methods or even store your view models in the database if you wish (although i think this might be a bit extreme).
Edit: Caliburn.Micro isn't a business application framework and there have been no library that tried to integrate business functionality with CM as far as i know, so this leaves you with serialization as your best option but as i said ser/des comes with some nightmares you have to manage such as version changes, class changes, etc.
There's another project called Catel which is a business application framework that contains an MVVM framework, anyway Catel uses a nice object called DataObjectBase ( actually now it is called ModelBase) which solves all problems of serialization and there is an article for that on code project if you want to read it and see how they have done it.
If you wish you can use the Catel.Core module which is a library with a lot of features for data handling (it contains the ModelBase class) or you can take a look at the source code and see how they have solved the issue with ser/des and implement that with Caliburn.Micro in your project.

COM+ Methods (How to Look Inside?)

I'm having to update one of our ancient Intranet applications that was written in Classic ASP and utilizes an in-house COM+ Service. I cannot find the source code to this object anywhere and it was not documented by the developer.
I can view the methods available in the Service through Start -> Administrative Tools -> Component Services but can't for the life of me figure out how to look inside the methods to see what they're doing.
Is there anyway to decompile these COM+ Services, or otherwise see what their methods do, or am I doomed to pure observation of the old application and try my best to mimic the behavior and data?
Note: I exported the service from the old server, installed in on my dev box, added the reference to a VS2010 project, and tried to discern these methods using the Object Explorer. Nothing...
COM services include type descriptions of what methods exist on the COM classes and their parameters so that automation controllers can figure out how to pass parameters to the COM methods.
Beyond that, though, there is nothing to indicate what the COM classes do internally other than the native x86 machine code itself. You can try using an x86 disassembler on the DLL, but unless you are already familiar with x86 machine code instructions, this won't be a lot of help.
Compiling source code down to native machine code throws away an enormous amount of information. Variable names, internal function names, none of that is needed for the CPU to execute instructions and perform the operations indicated by the original source code. It is virtually impossible for disassemblers to reconstitute these names that would be helpful clues as to what the code is intended to do. A disassembler can sometimes help figure out core logic, but it will require a lot of careful analysis and effort by a person to even scratch the surface. It's like trying to understand the forest by looking at individual blades of grass.

How to use SimpleMembership in MVC without Entity Framework

What are the required steps to use SimpleMembership (ASP.NET MVC 4) with RavenDB (or other databases) instead of SQL Server?
I am used to override the MembershipProvider but how does it work with the new SimpleMembership?
I saw there is a SimpleMembershipProvider so I think I should override it, but I don't know if the methods are for storing data purpose only or if they should contain business/validation logic)...
What about configuration? I know the InitializeDatabaseConnection method is normally responsible for initializing the whole shebang, but I don't think I should call it if I don't use Entity Framework.
Unfortunately, I did not find a lot of resources about the new SimpleMembership except two links which have not been very useful:
http://igambin.blogspot.ca/2012/08/simplemembershipprovider-huh.html
http://blog.osbornm.com/archive/2010/07/21/using-simplemembership-with-asp.net-webpages.aspx
So here is what I found after looking at some of the the source code (MVC4).
http://aspnetwebstack.codeplex.com/SourceControl/changeset/view/553690ac9488#src%2fWebMatrix.WebData%2fExtendedMembershipProvider.cs
SimpleMembership is an implementation of the abstract class ExtendedMembershipProvider.
The code inside SimpleMembership is mostly SQL operations and some calls to the underlying (called "previous" in the documentation) MembershipProvider.
I don't think it is of any use (in my case) to override SimpleMembership as its implementation is mostly tied to SQL Server. Instead, for what I understand, I should implement ExtendedMembershipProvider. Then, by setting this implementation in the web.config file, the WebSecurity helper would bypass SimpleMembership (default implementation) and call my implementation of the ExtendedMembershipProvider.
I don't think I will do this any soon since it looks even more complicated than before (more methods to implement)... but still doable.
However, all this said, I'm a bit disappointed that we still have to work with the MembershipProvider which, IMHO, is far (a lot of static and internal stuff) from the whole dependency injection thing that we love so much with ASP.Net MVC/WebApi.
Edit 1
This question was aked before Jon Galloway wrote this tutorial :
http://weblogs.asp.net/jgalloway/archive/2012/08/29/simplemembership-membership-providers-universal-providers-and-the-new-asp-net-4-5-web-forms-and-asp-net-mvc-4-templates.aspx
But my answer stays valid as this (taken from Jon Galloway article) resumes it:
Note that SimpleMembership still requires some flavor of SQL Server -
it won't work with MySQL, NoSQL databases, etc. You can take a look at
the code in WebMatrix.WebData.dll using a tool like ILSpy if you'd
like to see why - there are places where SQL Server specific SQL
statements are being executed, especially when creating and
initializing tables. It seems like you might be able to work with
another database if you created the tables separately, but I haven't
tried it and it's not supported at this point.
Here's my implementation for mongodb. Maybe it can help
https://github.com/malibeg/MongodbSimpleMembershipProvider#readme
SimpleMembership is not really meant to be used with the old MembershipProviders as it doesn't fullfill all of the same contracts that are assumed of normal MembershipProviders. Its mostly designed for use via the WebSecurity helper.
This link might be helpful for more info: Web Pages Tutorial

Using SqlCe as a database and unit tests with Sqlite

At the moment I am using SqlCe as a database for my project and doing unit tests with Sqlite because of its simplicity(Such as allow to use Inmemory). I just wonder, in the future this may lead to a dispute or oddity?
If using a different persistence mechanism inside of your unit tests causes you a problem, then the problem would likely be caused by:
Your unit tests
Your general application architecture
The tests that you write for an object should not depend on any way that their dependencies are implemented, doing so automatically means your unit tests turn into integration tests.
You should design your objects using the concept of Persistence Ignorance, which means that they are implemented in such a way so that their implementation does not depend on how the underlying datasource is implemented. A common method for achieving PI inside of enterprise applications is to use the Repository Pattern. This abstracts the interface your objects use to access the datasource from the underlying implementation of the datasource itself. What this means is, in theory, you can create new providers to different datasources without having to change the implementation of your objects that depend on them.
For example:
Let's say that you have an entity called Customer which you save inside of a SqlCe database. You could create an interface called ICustomerRepository that is implemented by a SqlCeCustomerRepository which you use inside of your main application. That way in your unit tests, you could swap it out for a SqlLiteCustomerRepository if you found that to be an easy way to create a mock datasource. To keep things even simpler, you could just create an InMemoryCustomerRepository that used List<T> under the hood to store and retrieve your objects. The point being it doesn't really matter HOW the datasource is implemented, as long as it conforms to the contract you set up on your repository interface.
The benefits of this pattern also reach beyond unit testing, and into general maintenance of your application. Suppose you want to scale up your architecture and use SQL Server instead of SQL CE, using an abstraction such as a repository would help limit the amount of change required in your system in order for this to happen, leading to less development time, less bugs, and happier customers.

Options for wiring dependencies with NInject

With NInject (preferably 2.0), what options do we have wrt wiring up our object dependencies in a web application?
Can they be defined in an XML configuration file?
Or does it have to be done via code?
There is an extension for xml based configuration: https://github.com/ninject/ninject.extensions.xml
You can do a lot more powerful binding in code though.
Ninject doesn't have XML configuration, sorry but I can't provide a direct link (cos their site has flash elements), but here is a quotation from ninject.org:
Free yourself from XML
Most other .NET dependency injection
frameworks are designed around the use
of XML to declare type bindings.
Rather than forcing you to write
cumbersome and error-prone text,
Ninject arms you with a fluent
interface, which lets you connect the
pieces of your application using
full-fledged code. This means you can
take advantage of the features of the
IDE and compiler, like code completion
and type-safety.
The problem I see with defining bindings in the code only is that you have to add reference to the dll.
You cannot change the binding without adding reference to new dll (removing reference to old one), change code and recompile.
If we had xml config I wouldn't need reference at all, and wouldn't have to recompile.
Right now I have MVC app that is using DI to pass repositories to Controllers. Nothing else then Ninject code for adding bindings uses the concrete implementations of repositories. And still I need to add reference to dll containing the implementations. For only one line of code!
Or maybe there is a possibility to achieve this using Ninject?
What are you looking to achieve? What sort of stuff are you looking to configure? Dynamically selecting a Strategy ? Passing in Port numbers? You could offer a lot more information as to what you're thinking in order to get a better answer [that you can acccept :P].
You need to split the concerns of:
known object wiring (DI)
configuration - generally you'll want to split those into small focused subsets e.g. Strongly Typed config elements vs having a global pool of settings in a big pile mishmashed together a la appSettings
plugins / unknown object wiring (MEF?)
In the first pool, doing it in Code is just the right way and I cant think of any advantage XML would give, esp. in the context of strong names etc.

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